This invention relates to sealing strips and concerns a sealing strip for preventing or reducing gas flow in an unwanted direction through an elongate gap, such as a gap between a door or window and its associated frame, and also concerns a method of preventing or reducing gas flow in an unwanted direction through an elongate gap.
Windows and doors are a notorious source of heat loss in houses and other buildings. There are two main ways by which such heat loss occurs: there is direct heat loss caused by conduction through the structural material of the window or door; and there is heat loss caused by the flow into the building of cold draughts that pass through any gaps between a door or window and its associated frame.
Heat losses caused by draughts are almost inevitable because it is very difficult as a practical matter to provide doors and windows that are a perfect sealing fit in their frames. Further, in the case of sash windows it is generally necessary to provide a clearance gap between the window sash and frame in order that the window can be slid open and closed.
As an illustration of the possible magnitude of heat losses resulting from such a clearance gap, consider a single element of a sash window measuring 38 in.times.34 in (0.97 m.times.0.86 m). A clearance between the sash and window frame of 0.015 in (0.38 mm) provides a total draught area of 2.16 in.sup.2 (13.9 cm.sup.2), that is approximately equivalent to the area of a circular hole 1.66 in (42 mm) in diameter.
Such a gap is thus capable of allowing a draught flow therethrough of approximately 2 ft.sup.3 (0.057 m.sup.3) per minute, at a notional pressure differential of 0.5 lb/in.sup.2 (3.4.times.10.sup.3 N/m.sup.2).
In an attempt to diminish heat losses caused by draughts, various expedients have been adopted to improve the fit between doors or windows and their frames and reduce the area of gaps therebetween.
For example, it is well known to secure strips of crushable material, such as foam plastic, to an appropriate surface of a door, window or frame. Such a strip may be fitted during construction of a door or window, for example by being embedded in the frame of a sash window. Alternatively, such a strip may be fitted to existing windows or doors, usually by means of adhesive. The use of such strips has various disadvantages. For example, they hinder the free sliding of sash windows. Further, such a strip can only be used in circumstances in which there is a sufficiently large gap between the door or window and frame to accommodate the strip and sometimes, particularly with casement windows, a sufficiently large gap is not available.
It is also well known to attempt to improve the sealing of doors and windows by the use of strips of relatively rigid, resilient material, including metals such as bronze, and suitable plastics materials. One edge of such a strip is secured, for example by means of tacks or pins, to an appropriate surface of a door, window or frame, the strip being provided with a raised free edge that extends towards an associated surface of a door etc. for engagement and depression thereby when the door or window is closed. Such strips are found to be fairly effective in reducing draughts, but do not form a perfect seal, partly because of the necessary rigidity of the strip material and its consequent inability to conform exactly with the surface it engages. Further, in some cases the use of such strips hinders the opening and closing of doors and windows.